An inkjet head serving as a liquid discharging device changes ink pressure within a pressure chamber, causes the ink to flow, and discharges ink from a discharge opening, thereby spraying liquid droplets. Particularly, a drop on demand type of head is most generally used. Also, methods to apply pressure to the ink are largely divided into two methods. These are a method to change the pressure of the ink by changing the pressure within the pressure chamber with a driving signal to the piezoelectric elements, and a method to add cause bubbles to occur within the pressure chamber with a driving signal to a resistor, thereby applying pressure to the ink
An inkjet head using piezoelectric elements can be created relatively easily by mechanically processing piezoelectric materials in bulk. Also, there is the advantage of having relatively few limits to the ink and being able to selectively coat the recording medium with inks of a wide variety of materials. From such a perspective, recently efforts have increased to use inkjet heads in industrial applications such as the manufacturing of color filters, forming wiring, and so forth.
Of the piezoelectric methods of inkjet heads used industrially, a share mode method is frequently employed. The share mode method uses shear deformation by applying an electrical field to the piezoelectric elements, which have been subjected to polarization treatment, in an orthogonal direction. The piezoelectric elements to be deformed are, for example, the dividing wall portion that is formed by processing an ink groove or the like with a dicing blade in the bulk piezoelectric materials that have been subjected to polarization treatment. On both sides of the piezoelectric elements which are the dividing wall thereof, electrodes to driving the piezoelectric elements are formed, and a nozzle plate on which a nozzle is formed and an ink supply system are formed, whereby an inkjet head is configured (see PTL 1). Such a share mode method inkjet head can be relatively easily manufactured.
In recent years, there have been demand for higher liquid discharge capability of share mode method inkjet heads. Specifically, capability to discharge droplets having higher viscosity at a higher speed, and to discharge more minute droplets, are demanded. In order to do so, piezoelectric elements, which make up a share mode method inkjet head, that are subjected to shear deformation at a higher speed and droplets are applied instantaneously, are demanded.
That is to say, with a share mode method inkjet head, in order to increase the droplet discharge speed, the piezoelectric element displacement energy is increased, and the pressure change within the pressure chamber has to be increased. Therefore, the frequency properties of the piezoelectric elements which are defined by the product of the amount of shear deformation and vibration properties, which is a feature relating to the deformation energy of the piezoelectric elements, has to be increased.